memcontrol04: Fix the judgment error in test_memcg_low()

In the test_memcg_low() function, 4 subgroups (C, D, E, F) are created under B,
and 50MB pagecache is allocated in C, D, and F. Therefore, when checking whether
it is successful at the end, only E should be judged to have low_events==0,
and the judgment conditions for all other subgroups should be low_events > 0.

Fix issure: linux-test-project#1209
linux-test-project#1209

testcases/kernel/controllers/memcg/memcontrol04.c

@@ -207,7 +207,7 @@ static void test_memcg_low(void)
 
 		TST_EXP_EXPR(oom == 0, "(%c oom events=%ld) == 0", id, oom);
 
-		if (i < E) {
+		if (i != E) {
 			TST_EXP_EXPR(low > 0,
 				     "(%c low events=%ld) > 0", id, low);
 		} else {